358 
Mr . Oslee on burrowing 
I was shown two specimens which had been taken out of 
a pile many years before, but they were treasured as a 
curiosity ; and I was assured by Mr. Churchill, the master 
shipwright, that at present they are never met with. The 
shipping of Swansea trade to every part of the kingdom, and 
we have nearly four thousand arrivals in the year, chiefly 
from coasting voyages ; but, though very few of the vessels 
are coppered, we never see the Teredo. 
Two causes may be assigned for this complete destruction, 
either of which appears sufficient to account for it. An 
imported shell-fish, if pelagic, may naturalize itself perma- 
nently ; but where, like the Teredo, it always resides near the 
surface, and often in situations which are left dry during the 
ebb, it is necessarily affected by changes of temperature ; and 
the animal which is naturally the inhabitant of a warm 
climate, will be destroyed by a severe winter. It is probable 
that the Teredo was formerly preserved only by occasional 
importations, which are now prevented by the general use of 
copper sheathing. 
Independent of causes connected with climate, the Teredo 
would diminish, and become extinct for want of a nidus. 
Where piles had been destroyed by them, care would be taken 
to preserve the new ones from their ravages by a covering 
which the young animals cannot penetrate. Valuable timber 
would not be placed within their reach ; and wood, neglected 
because useless, is generally too small to contain a large 
Teredo. They would therefore perish from confinement be- 
fore they were full grown. The Pholas dactylus, which, but 
a few years since, was very numerous in Swansea bay, has 
been lost here from this cause. The large beds of peat-wood. 
